As an alternative to Public Switched Telephone Network (PSTN) systems, cellular phone networks have proliferated over the last decade where users with cellular phones have access to one or more networks at almost any location. Also a recent development is the wide spread use of Voice over IP (VoIP) telephony, which uses internet protocol over wired and wireless networks. With the availability of such diverse types of communication networks and devices capable of taking advantage of various features of these networks, a new technology is bringing different communication networks together providing until now unavailable functionality such as combining various modes of communication (e.g. instant messaging, voice calls, video communications, etc.). This technology is referred to as unified communications (UC). A network of servers manages end devices capable of handling a wide range of functionality and communication while facilitating communications between the more modern unified communication network devices and other networks (e.g. PSTN, cellular, etc.).
In addition to accommodating various modes of communication, modern real time communication systems such as UC systems can facilitate presence and routing capabilities, which basically enable a user to place and receive calls (in any communication form) through a number of end devices regardless of physical location. For example, a user may define a destination number (identifier), where he/she can be reached at different times or depending on the context of the call, and the system is capable of routing the call based on the user provided rules.
When a call is made ringing multiple user end devices or applications (i.e. forking) and one of the endpoints answer, the ringing is stopped at all other stations. This is an example of a situation where a request is forked, then answered in a station, which results in a cancellation of the forked requests at all other stations. Another example of request cancellation is when one of the endpoints declines the request globally resulting in all the other forked requests getting cancelled. In conventional systems, the endpoints where the call request is cancelled may not know why the cancellation occurred.